Recent analyses of the transcriptional output of mammalian genomes have revealed the presence of a significant number of novel long non-protein-coding (Inc) RNAs. Although many lncRNAs show a tissue or developmental stage-specific expression pattern that is conserved across different species, the question of whether the majority of this class of transcripts have any cellular function whatsoever remains the subject of intense debate. Most mysterious are the long intergenic non-coding RNAs, a class of transcripts derived from genomic regions located far away from known genes, which have remained highly understudied.
Interestingly, a substantial fraction of the cellular lncRNAs, including intergenic lncRNAs, are expressed in the brain and other neural tissues. Although few studies have addressed the roles of these transcripts in the development and function of the nervous system, current data point to diverse regulatory functions for lncRNAs in brain, ranging from regulating expression of homeobox proteins and development of neuronal GABAergic circuitry to regulating biogenesis of RNAs involved in synaptic function. Although these studies, together with analyses of lncRNA function in non-neuronal cells, suggest that this class of RNA molecules participates in virtually every aspect of cellular function, the overall importance of lncRNA-mediated regulation for cellular and organismal function remains controversial.